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Using A Taper Attachment.

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Alan .20425/05/2019 14:47:59
304 forum posts
14 photos

So far after doing some adjustments on the lathe gibs and also checking the gibs on the taper attachment I used a piece of scrap mild steel and cut an 8 degree taper for my ER collets, every thing went realy well, so next was to make it for real and then the problem has started, the steel I have is I think called SS99 it’s as hard as hell but I went nice and steady managed to internally thread 1/500 x 8tpi I made a carbide threading bar to do it, cutting the taper how ever hasn’t turned out well at all, the finish in the bore is shite to be honest the only thing that’s different is the steel, very tough to turn, when turning the taper I’m going in the conventional manor ie right to left and normal rotation of the lathe, my question is would I get on better if I was using a right hand tool turning the back of the bore so to speak with the lathe spindle running in reverse, I’m thinking of backlash if there is any in the taper attachment, think of it like climb milling on a conventional mill, hope ive made sense, I’ll continue with this part as it only needs the threads for the collet nut so I may as well finish it, should have said that I’ve tried all manor of different boring tools on this and there’s realy no difference in the finish, best I can describe it is it has ridges along the bore, even after a realy sharp carbide boring bars been through taking 0.1 mm cut them a spring pass also both at speeds ranging from 130 / 425 rpm at .001 feed rate,

Thanks Alan.

Andrew Johnston25/05/2019 15:07:11
4855 forum posts
544 photos

Hmmm, S99 is a nickel/chrome/moly high carbon steel intended for aerospace. I expect that the combination of slow speed, low depth of cut and tiny feedrate simply doesn't cut it. I'd suggest a feedrate of 0.1mm/min upwards, DOC of 0.25mm upwards depending upon the tool geometry, and 1500+ rpm.


Alan .20425/05/2019 15:21:35
304 forum posts
14 photos

That’s the stuff Andrew saying as hard he’ll minght not be the right phrase more like just tough, I’ll try increasing speed and feed if it doesn’t work out I’ve managed to find some mild steel that shoul do the job, you know what it’s like you find a piece the right size and think that will do just fine 🤔 any way positives are I’ve had plenty of practice with the taper attachment and learnt a lot along the way so all good.

Thanks Andrew, Alan.

Alan .20425/05/2019 19:13:07
304 forum posts
14 photos

Worked a treat Andrew, lovely finish in the taper bore 1800 rpm 4thou feed rate. 20 depth of cut, that saved the part, thanks for the advice.


John Paton 126/05/2019 00:52:02
172 forum posts
6 photos

Just reaffirms the value of this site to us mere mortals - there are 'Gods' in here who really know their stuff so it's always worth asking!

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